Yes, the Actiontec Routers and Modems support File and Printer Sharing.
No, it does not require enabling. There are no settings on the Actiontec routers and modems with regard to sharing, it is the router's default behavior. All of the settings for sharing are on the computers (or printers, or NAS, etc...) themselves.
The Actiontec routers and modems do not have any additional features or settings for File and Printer Sharing (computers that can 'see each other' or a networked printer on the network). As stated earlier, the default behavior of the Actiontec allows this activity with no restrictions. Wireless devices have access to each other and to wired devices, whether Ethernet or USB. The reverse is also true, wired devices (like a PC) have full access to other wired devices (like a printer or NAS), as well as wireless devices (whether PC or printer).
Provided that the PCs in question have a functioning Internet connection through the Actiontec router or modem. Then...
If a device can not 'see' the network or access resources on the network, the cause will be on the devices themselves. If it is a printer, then it may be a network TCP/IP setting or missing protocol. If it is a server or workstation that cannot be accessed, then it will be TCP/IP settings, firewall settings or misconfigured sharing on the PC.
The bottom line is this, there are NO settings on the Actiontec routers and modems for sharing.